Lithium ion flow battery is a newly developed chemical battery technology, which integrates the advantages of lithium ion battery and flow battery, and thus becomes a novel rechargeable battery with independent power output and energy storage capacity, high energy density and low cost. Lithium ion flow battery has tremendously wide market prospects in wind power generation, photovoltaic power generation, power grid peak load regulation, power station distribution, municipal transportation and the like.
Lithium ion flow battery is composed of a cathode suspension solution tank, an anode suspension solution tank, a battery reactor, a liquid pump or pneumatic control system, and sealed conduits, wherein the cathode suspension solution tank contains a mixture of cathode materials particles, a conductive additive and an electrolyte, and the anode suspension solution tank contains a mixture of anode materials particles, a conductive additive and an electrolyte. The structure of a lithium ion flow battery reactor comprises: a cathode current collector, a cathode reaction chamber, a cathode liquid inlet, a cathode liquid outlet, a separator, an anode current collector, an anode reaction chamber, an anode liquid inlet and an anode liquid outlet. The cathode suspension solution flows into the cathode reaction chamber of the battery reactor via the cathode liquid inlet, flows out via the cathode liquid outlet after the reaction is completed, and returns to the cathode suspension solution tank through sealed conduits under the action of the liquid pump propulsion or pneumatic control system; and meanwhile, the anode suspension solution flows into the anode reaction chamber of the battery reactor via the anode liquid inlet, flows out via the anode liquid outlet after the reaction is completed, and returns to the anode suspension solution tank through the sealed pipelines under the action of the liquid pump propulsion or pneumatic control system.
The battery reaction chamber is an important component of a lithium ion flow battery reactor, wherein an electrode suspension solution flows intermittently or continuously within the battery reaction chamber to complete the charge-discharge reaction of the battery, and an electron-nonconductive separator is provided between the cathode reaction chamber and the anode reaction chamber of the lithium ion flow battery reactor, such that conductive particles in the cathode suspension solution (particles of cathode active materials and particles of conductive additives) and those in the anode suspension solution (particles of anode active materials and particles of conductive additives) are separated from each other to avoid short circuit occurred within the battery caused by direct contact of the conductive particles.
Compared with the electrolyte of an all-vanadium redox flow battery, the electrode suspension solution of the lithium ion flow battery is more viscous and relatively more difficult to flow, thus there is a high requirement on design for the reaction chamber of the battery reactor, in which case an excessively narrow reaction chamber could be detrimental to the flow of the electrode suspension solution. Previously, the structure of a lithium ion flow battery reactor is generally designed such that: several separators are arranged in parallel equidistantly, the space therebetween alternately constituting the cathode reaction chambers and the anode reaction chambers, wherein a cathode current collector is located in the middle of the cathode reaction chamber, and cathode suspension solution continuously or intermittently flows within the gap between the cathode current collector and the separator; an anode current collector is located in the middle of the anode reaction chamber, and anode suspension solution continuously or intermittently flows within the gap between the anode current collector and the separator, as shown in FIG. 1. In other words, the gaps between the current collectors and the separators form an electrochemical reaction chamber of the battery. When the battery is working, the cathode suspension solution (16) continuously or intermittently flows within the gap space between the cathode current collector (11) within the cathode reaction chamber (14) and the separator (13), and electrons transfer between the cathode suspension solution (16) and the cathode current collector (11); similarly, the anode suspension solution (17) continuously or intermittently flows within the gap space between the anode current collector (12) within the anode reaction chamber (15) and the separator (13), and electrons transfer between the anode suspension solution (17) and the anode current collector (12); and lithium ions are exchanged and transmitted between the cathode suspension solution (16) within the cathode reaction chamber and the anode suspension solution (17) within the anode reaction chamber through the separator (13).
The problem existing in the above design is that, taking into account the fluidity of electrode suspension solution, the larger the gap distance between the current collector and the separator is (i.e., the larger the space of the reaction chamber is), the more easily the viscous electrode suspension solution flows, otherwise too small gap distance will make the electrode suspension solution flow difficulty; while taking into account the polarization resistance, the smaller the gap distance between the current collector and the separator is (i.e., the smaller the space of the reaction chamber is), the smaller the current collecting internal resistance is, otherwise too large gap distance will increase the conductive distance of electrons and ions in the electrode suspension solution, thereby increasing the internal resistance of the battery and lowering the charge-discharge conversion efficiency. Therefore, the above interacting factors restrict the design flexibility for dimension of the reaction chamber, and affect the performance of the lithium ion flow battery.